18 
THE YOUNa SCIENTIST. 
Simple Lessons in the Art of Photo- 
graphy. 
rpHE art of photography is one capable 
of affording a great deal of interest and 
pleasure, and some departments, and these, 
perhaps, the most pleasing, are so readily 
learned that we feel confident that if our 
readers only understood how simple it is, 
many of them would adopt it as a recrea- 
tion. By it our summer wanderings and 
excursions may be enlivened, and the pleas- 
ant memories surrounding them may be 
perpetuated by views of the places and ob- 
jects which we have visited. Truthful views 
of such objects as apparatus, machines, 
specimens of natural history, and various 
other objects may be taken either for trans- 
mission to distant friends, or for future 
reference and study. And with the ad- 
vances which have of late years been made 
in the manufacture of simple forms of ap- 
paratus and fine qualities of material, the 
outfit required for commencing the prac- 
tice of the art is not by any means expen- 
sive. We hope, therefore, to see ere long a 
large number of amateur photographic 
clubs organized all over the country. These 
clubs, by mutual intercourse between the 
members, will smooth the path of learners 
and greatly increase the interest and profit 
of the occupation by promoting exchanges. 
And we would remind such clubs that our 
exchange column is always open to them 
free of charge. 
These photographic clubs are not by any 
means a novel suggestion. In England and 
Scotland they flourished extensively twenty 
years ago, and, we believe, many of them 
are still existing in a prosperous condition. 
In order to give those of our readers who 
have a taste in that direction an opportu- 
nity to make a commencement, we propose 
to explain in simple terms the principles of 
the art, and the rules for putting them in 
practice. 
The art of photography depends for its 
success upon the changes which light pro- 
duces in certain chemical compounds — par- 
ticularly the salts or combinations of silver. 
These photographic effects of light are^ 
however, produced with great power by but 
one of the three beams into which a ray of 
white light may be separated by a prism» 
These three beams give rise to the colors 
known as yellow, red and blue, and it is the 
blue ray that possesses in the highest de- 
gree what is called the actinic, or chemical 
power. The red ray is not nearly so ef- 
ficient, and the yellow ray has scarcely any 
chemical power at all. Consequently, a* 
room may be almost dark, from being feebly 
illuminated with powerful blue rays, and 
yet be very powerfully lit up, photograph- 
ically speaking; while another may be quite 
well lighted, so far as mere vision is con- 
cerned, and yet be photographically dark, 
from the fact that the rays of light are all 
yellow, the blue rays having been excluded. 
These facts are very important, as we shall 
see when we come to give directions for 
arranging the work room, or dark room, a& 
it is generally called. 
Of the numberless processes for producing 
pictures, we propose to describe only one 
particular method, the collodion process, 
which is not only easily understood, but 
which also produces, with a comparatively 
small amount of study and experimentation, 
the finest results. 
Pictures by the collodion process are 
taken either on glass or ferro-plates. They 
are called positives or negatives, according 
to the degree of exposure and development 
to which they have been subjected. Good 
ferrotypes or pictures taken on ferro-plates, 
are always good positives; but a good nega- 
tive would make a poor positive. In a 
positive the collodion film is thin, and the 
silver deposit rather transparent, so that 
reflected light will clearly show all minute 
details. A negative is a positive to a cer- 
tain extent, but the deposit of silver on the 
parts acted on by light is considerably 
denser, and the details of the picture can 
only be detected by transmitted light. 
Beginners in photography should com- 
mence by making positives, either glass pos- 
itives or ferrotypes, since this process con^ 
